Looks like there isn't a way to protect (or semiprotect) completely a talk page with LiquidThreads, e.g. an archived talk: even if you use [edit=sysop] [move=sysop] [newthread=sysop] [reply=sysop] [cascading] , users will be able to edit existing replies (but not to summarize threads, if my test was correct).
I haven't tried all the other possibile actions, but I think that at least cascading protection (or something similar) should block them all.

Otherwise, it's impossible to protect pages from vandalism and even from good faith edits; while currently, if you archive a page, you put the archive in your watchlist and if someone edits it you will see it immediately; with threads it isn't so easy, although I don't remember if watchlisting a talk page will watchlist every included thread).

Version: unspecified
Severity: enhancement